So-called projectors have been used as an apparatus for projecting an image on a wall or a screen. When a presentation is made, for example, a lecturer sometimes points to an object, e.g., a character or a figure, that is present in an image being projected by a projector by using a tool such as a laser pointer. For example, Patent Literature 1 discloses a conference assisting method of receiving, when a video being projected on a screen is irradiated with light from a light-emitting pointer, reflection light of the light from the light-emitting pointer and detecting the track of the light from the light-emitting pointer, so as to perform display corresponding to the track of the light on the screen.